Noise and low frequency vibration may be created in commercial aircraft by a variety of sources. For example, exterior noise may be created by air passing over the aircraft's outer skin in a turbulent boundary layer. Also, wing mounted engines may excite low frequency vibration modes of the aircraft's fuselage. This vibration energy may be transmitted through the fuselage by stringers and frames and enter into the cabin interior as noise.
One solution for reducing noise and vibration involves the use of damping treatments such as “add-on” patches of viscoelastic materials which absorb and dampen noise and vibration. These add-on patches are essentially “peel and stick” components that are added to various parts of the aircraft, such as skins, frames and floor panels. A typical commercial aircraft may employ as many as 2500 to 3500 of these patches. While effective in reducing noise and vibration, the patches add weight to the aircraft and are labor intensive to install.
Accordingly, there is a need for a composite structure having inherent damping qualities that reduce or eliminate the need for add-on damping treatments of the type mentioned above. Embodiments of the disclosure are intended to satisfy this need.